One sentence lit a fast-moving firestorm today today on the presidential campaign on the topic of women and the right to choose aboorgs after a rape. It all started with a statement by a republican candidate for the senate. Here's what he said, that it's harder for women to get pregnant after what he called a legitimate rape. The president made a surprise appearance at the white house challenging the romney/ryan ticket. And "your voice your vote" here's david muir tonight with the sentence that starts it all, david. Reporter: Diane, good evening. The president centering a huge opening among women voters. After a controversial words about that member running for senate, eye-opening words about abortion. The president using those words to go after mitt romney and his running mate. The next vice president of the united states! Reporter: Mitt romney was about to take the stage with his running mate. It all started with the controversial comment made by a little-known republican congressman running for senate in missouri. But his comment would suddenly light a national fuse over the women's right to choose. The romney team reacting. That congressman was reiterating in cases of rape going further saying women's bodies have a way of working, a way to stop pregnancy during rape. It seems to me first of all what I understand from doctors, that's really rare. If it's a lechts rape, the female body has ways to try to shut that whole thing down. Reporter: The reason it's ricocheted all the way to the white house is because that congressman has often seen eye to eye with mitt romney's running mate. On a bill on abortion, one bill that would offer exception of abortion in races of rape. The president sensing an open, trying to reach women voters saying no matter what that congressman in missouri is trying to say, the president was on the other side. His view expressed were offensive. Rape is rape. And the idea that we should be parsing and qualifying and slicing what types of rain we're talking about doesn't make sense to the american people. And certainly, doesn't make sense to me. Reporter: The presi goi even further, asking why men in congress are deciding for women. What I think these comments do underscore is why we shouldn't have a bunch of politicians, a majority of whom are men, making health care decisions on behal women. Reporter: The romney campaign saying today a romney/line administration would not oppose abortion. Romney calling akin's words insulting, inexcusable and frankly wrong. And while not asking him to drop out of the race, romney did say this to wmur today. What we believe, in the things that he believes in most deeply what will help the country at this point in time. In deciding how big an opportunity the president saw today, he appeared in that white house briefing room for the first time since the white house press corps since june. They were hoping to get back to jobs and the economy today, diane. Thank you, david. A direct challenge to women voters, as you say.

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